This invention relates to a point detection system for a railway switch machine and an associated method of point detection for a railway switch machine.
As is known in the art, a common method for switching a train from one railroad track to another is to install an electric motor driven switch machine next to the switching point of the track. Current versions of these switch machines are typically operated from a remote location, therefore it is essential that a remote operator be able to determine the position of the switch. In addition, because switch point closure is imperative to safe railroad train operation, Federal Railroad Administration (FRA) rules and regulations mandate not only that the position of the switch points be mechanically locked to prevent the points from opening during train traffic but also that the locked position of the switch points be continuously monitored to detect any undesirable movement.
Prior art switch machines relied on mechanical devices to perform the point and lock detections. However, such mechanical arrangements were subject to degradation over time as a result of wear. In addition, other factors, such as weather, directly affected the reliability of such systems.
U.S. Pat. No. 5,806,809 discloses a railroad switch point position detecting system employing a plurality of proximity detectors positioned proximate to the switch point or points of a railroad switch. These proximity detectors for detecting switch point position are physically located on the switch points or corresponding stock rail. While the use of proximity detectors in general are an improvement over the previous mechanical systems, there are still noted shortcomings of the use thereof. For example, the proximity sensors employed by the '809 patent provides no means to distinguish ON from shorted and OFF from open. Therefore, in a static situation, an ON sensor that shorts will go undetected. If the switch points were subsequently forced open, as would occur with a train running through in the wrong direction, it would go undetected. With the switch points forced open and not reflected in the indication circuit, a safety hazard is created.
There remains a need, therefore, for a point detection system for a railway switch machine that overcomes the disadvantages and shortcomings of the prior art and provides a safe and reliable means for detecting point position.